FIG. 1 is a block diagram illustrating an example architecture for a Long Term Evolution (LTE) mobile communication system 100, also referred to as Evolved Packet System (EPS) or 4G. LTE architecture introduces several new service elements, compared to other mobile communication systems' architecture, such as the Mobility Management Entity (MME) 101, the control node which processes the signaling between the User Equipment (UE) and the Core Network (CN) and provides Visitor Location Register (VLR) functionality for the EPS; the Serving Gateway (S-GW) 115, a gateway which terminates the interface towards the Evolved Universal Terrestrial Radio Access Network (E-UTRAN); the Packet Data Network (PDN) Gateway (P-GW) 117, a gateway which terminates the interface towards the Packet Data Network; the Policy Control and Charging Rules Function (PCRF) 107, which encompasses policy control decision and flow-based charging control functionalities; and the Home Subscriber Server (HSS) 103, an entity containing subscription-related information to support the network entities handling calls/sessions.
The communication or signaling between different elements of the LTE mobile communications system 100 generates a significant amount of traffic due to the new architecture and new procedures associated with its all-IP infrastructure. One of the key signaling protocols used is the Diameter protocol, an IP-based protocol employed over many interfaces, such as S6a interface 105, Gx interface 109, and Rx interface 111. Signaling or Diameter Signaling traffic is generated due to many actions initiated by the UE, such as requesting to access the network, and network defined procedures such as Track Area Update and retrieving user's service policies via Gx interface 109 at the P-GW 117, and so on.
Some of the signaling interfaces are extended to other LTE mobile communication systems or networks in order to fulfill LTE mobile roaming services when LTE UE access LTE services from a visited LTE Mobile Operator.
FIG. 2 is a block diagram depicting a LTE roaming reference architecture. As indicated in the block diagram, the signaling generated from the MME 101 at the visited mobile network over the S6a interface 105 and from the P-GW 117 over the Gx interface 109 are meant to reach the home network HSS 103a and home network PCRF (H-PCRF) 107a, respectively, during roaming. The H-PCRF 107a and the visited network PCRF (V-PCRF) 107b are coupled through an S9 interface 218. The S9 interface 218 bridges the local Gx signaling over the V-PCRF 107b to the H-PCRF 107a, where the users' service policies are defined and stored.
Given typical LTE architectures and the signaling associated with UE actions and LTE-defined procedures, LTE operators deploying LTE mobile systems may encounter overwhelming levels of Diameter and other IP-based signaling traffic such as GTP tunnel protocol used for establishing IP access for UE 113. Such signaling bursts are often referred to as a signaling storm. Some LTE networks have been brought down due to such signaling storms.
To mitigate signaling storm issues, a variety of solutions have been brought forth that focus on the signaling flow from UE 113, S-GW 115 and P-GW 117. For example, to optimize Diameter signaling operation and reduce full-mesh diameter connections among Diameter elements, e.g., the Diameter elements MME 101, HSS 103, P-GW 115, and PCRF 107a or 107b, etc., a central Diameter Agent (DA) or Diameter Routing Agent (DRA) may be introduced within the LTE core network to provide centralized routing, traffic management, and load balancing among Diameter elements. FIG. 3 shows two block diagrams illustrating a bilateral full-mesh architecture and centralized DA based architecture, respectively. The bilateral full-mesh architecture is not scalable as it involves coupling each pair of Diameter elements, e.g., 301-305, through a communication channel. In the centralized DA based architecture, a DA 310 is deployed within an LTE core network. The DA 310 is coupled to the Diameter elements, e.g., 301-305, and acts as a routing agent. The Diameter Element, e.g., 301-305, may be an element such as MME 101, HSS 103, P-GW 117, or the like. Likewise, a DA, or DRA, 310 may be deployed within an LTE roaming network coupling, for example, the MME 101 in the visited network and the HSS 103 in the home network. Typically, a DRA is provided in a third party network, which is connected to both the visited and home network, as intermediary service provider.